1. Field of the Invention
The present invention relates to a scale used for a displacement detection apparatus that detects a position of an object.
2. Description of the Related Art
Previously, as a unit of detecting a moving amount or a rotating amount of an object (an object to be measured), a displacement detection apparatus has been known. In addition, as the displacement detection apparatus, there is an optical-type, magnetic-type, or capacitance-type displacement detection apparatus, or the like. For example, the optical-type displacement detection apparatus is configured by including a light source, a scale that reflects or transmits light emitted from the light source to be able to be displaced relative to the light source, and a light receiving element that receives light reflected by or transmitting through the scale. A pattern that reflects or transmits light is formed on the optical scale, and a light amount received by the light receiving element changes depending on a relative displacement of the scale. The displacement is detected based on a detection signal generated by the change of the light amount by the light receiving element.
Japanese Patent No. 4360762 relates to a displacement detection apparatus, which discloses a configuration in which a light amount passing through an opening is detected to detect a relative alignment between a light receiving portion and a scale of the displacement detection apparatus. Japanese Patent No. 3473148 discloses a configuration in which a transit time of a wedge-shaped pattern is measured to detect a relative alignment between a sensor and a scale.
However, when an inexpensive light source such as an LED or an LD is used in the displacement detection apparatus disclosed in Japanese Patent No. 4360762, a lens for shaping a light beam is necessary. In the configuration disclosed in Japanese Patent No. 4360762, it is possible to detect a displacement from an optimum alignment state, but a direction of the displacement cannot be detected. In this configuration, in order to determine the direction of the displacement, further alight shielding member, a dedicated light receiving portion, or the like needs to be prepared. In the configuration disclosed in Japanese Patent No. 3473148, when the scale is displaced relative to the sensor in a direction perpendicular to a measurement direction, phase information of the measurement direction is influenced.